During the drilling of an oil or gas wellbore or the like, situations are encountered wherein a component of the drill string becomes lodged in the wellbore. When the static force necessary to move a drill string exceeds the rig's capabilities or the tensile strength of the drill pipe, the drill string is stuck and can no longer be moved or rotated. A jar is a tool that is prepositioned within the drill string to free any portion of the drill sting which may become stuck.